An elastic surface acoustic wave (SAW) device has been well known as a device to which elastic waves are applied. This SAW device is used for various kinds of circuits in a device for processing a radio signal in a frequency band of 45 MHz to 2 GHz. For example, SAW devices have been known for use in a transmission band pass filter, a reception band pass filter, a local oscillation filter, an antenna duplexer, an IF filter, an FM modulator, etc.
In connection with the enhancement in performance of cellular phones, etc., improvements of various characteristics such as reduction of loss within the band, high suppression at the outside of the band, enhancement of temperature stability, etc., and miniaturization of the device size have been recently required in SAW devices used as band pass filters. Particularly, the reduction of loss is related to the problem of increasing the driving time of cellular equipment which has been recently problematic, and it is a permanent object required to cellular equipment parts.